I assume you mean the
7028-6E1 (also known as the pSeries model 610).
According to the fact sheet, this model supports the 2.4 Linux kernel but I don't think you can assume that any given distro. will work. Red Hat and SuSE should both be OK, but I'm sure IBM doesn't officially support Mandrake or Yellow Dog.
I haven't yet tried installing Linux on pSeries but as far as I can tell, a supported distro should install OK from CD.